
public class TwoLinkList {
    static class Node {
        int val;
        Node next;
        Node prev;
        Node(int val) {
            this.val = val;
        }
    }
    Node head;
    Node last;
    //头插法
    public void addFirst(int data){
        Node node = new Node(data);
       if (head == null) {
           head = node;
           last = node;
           return;
       }
       node.next = head;
       head.prev = node;
       head = node;
    }
    //尾插法
    public void addLast(int data){
        Node node = new Node(data);
        if (head == null) {
            head = node;
            last = node;
            return;
        }
        node.prev = last;
        last.next = node;
        last = node;
    }
    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data){
        if (index < 0 || index > size()) {
            throw new PosOutOfRange();
        }
        if (index == 0) {
            addFirst(data);
            return;
        }
        if (index == size()) {
            addLast(data);
            return;
        }
        Node cur = head;
        int count = 0;
        while (count != index) {
            cur = cur.next;
            count++;
        }
        Node node = new Node(data);
        node.prev = cur.prev;
        node.next = cur;
        cur.prev.next = node;
        cur.prev = node;
    }
    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key){
        Node cur = head;
        while (cur != null) {
            if (cur.val == key)
                return true;
            cur = cur.next;
        }
        return false;
    }
    //删除第一次出现关键字为key的节点
    public void remove(int key){
        Node cur = head;
        while (cur != null) {
            if (cur.val == key) {
                //只有一个节点
                if (cur == head) {
                    head = head.next;
                    if (head != null) {
                        head.prev = null;
                    } else {
                        last = null;
                    }
                } else {
                    //中间节点
                    if (cur.next != null) {
                        cur.prev.next = cur.next;
                        cur.next.prev = cur.prev;
                    } else { //尾巴节点
                        cur.prev.next = cur.next;
                        last = cur.prev;
                    }
                }
                return;
            }else {
                cur = cur.next;
            }
        }
    }
    //删除所有值为key的节点
    public void removeAllKey(int key){
        Node cur = head;
        while (cur != null) {
            if (cur.val == key) {
                //只有一个节点
                if (cur == head) {
                    head = head.next;
                    if (head != null) {
                        head.prev = null;
                    } else {
                        last = null;
                    }
                } else {
                    //中间节点
                    if (cur.next != null) {
                        cur.prev.next = cur.next;
                        cur.next.prev = cur.prev;
                    } else { //尾巴节点
                        cur.prev.next = cur.next;
                        last = cur.prev;
                    }
                }
            }
           cur = cur.next;
        }
    }
    //得到单链表的长度
    public int size(){
        int count = 0;
        Node cur = head;
        while (cur != null) {
            cur = cur.next;
            count++;
        }
        return count;
    }
    public void display(){
        Node cur = head;
        while (cur != null) {
            System.out.print(cur.val + " ");
            cur = cur.next;
        }
        System.out.println();
    }
    public void display(Node head){
        Node cur = head;
        while (cur != null) {
            System.out.print(cur.val + " ");
            cur = cur.next;
        }
        System.out.println();
    }
    public void clear(){
//        head = last = null;
        Node cur = head;
        while (cur != null) {
            cur.prev = null;
            Node curNext = cur.next;
            cur.next = null;
            cur = curNext;
        }
        head = null;
        last = null;
    }
}
